The class of polymers of carbon monoxide and olefin(s) has been known for some time. Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of relatively low carbon monoxide content in the presence of free radical initiators, e.g. peroxy compounds. U.K. 1,081,304 produced similar polymers in the presence of alkylphosphine complexes of palladium salts as catalyst. Nozaki extended the reaction to produce linear alternating polymers in the presence of arylphosphine complexes of palladium moieties and certain inert solvents. See, for example, U.S. Pat. No. 3,694,412.
More recently, the class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon, now becoming known as polyketones or polyketone polymers, has become of greater interest in part because of the greater availability of the polymers. The more recent general processes for the production of the polymers is illustrated by a number of published European Patent Applications including 121,965, 181,014, 224,454 and 257,663. The process generally involves the use of a catalyst composition formed from a salt of a Group VIII metal selected from palladium, cobalt or nickel, the anion of a non-hydrohalogenic acid having a pKa below about 6, preferably below 2, and a bidentate ligand of phosphorus, arsenic or antimony.
The resulting polymers are relatively high molecular weight materials having established utility as premium thermoplastics. They are employed in the production of shaped articles, for example, as containers for food and drink, by methods such as extrusion, injection molding or thermoforming which are conventional for thermoplastics. Although the polyketone polymers process relatively easily with good retention of properties, they do undergo a certain degree of loss of desirable properties when such processing includes one or even more than one cycle of melting and solidification. It would therefore be of advantage to provide a method by which such loss of desirable properties is minimized and an improved melt stability is observed during the melt/solidification processing of the polyketone polymers.